Microelectronic imagers are used in digital cameras, wireless devices with picture-taking capabilities, and many other applications. Mobile phones and personal digital assistants (PDAs), for example, are incorporating microelectronic imagers for capturing and sending pictures. The growth rate of microelectronic imagers has been steadily increasing as they become smaller and produce better images with higher resolution.
Microelectronic imagers include image sensors that typically use charged coupled device (CCD) systems or complementary metal-oxide semiconductor (CMOS) systems, as well as other systems. CCD image sensors have been widely used in digital cameras and other applications. CMOS image sensors are also quickly becoming very popular because they have low production costs, high yields, and small sizes.
As shown in FIG. 1, microelectronic imager modules 150 are often fabricated at a wafer level. The imager module 150 includes an imager die 108, which includes an imager array 106 and associated circuits. The imager array 106 may be a CCD or CMOS imager array, or any other type of solid state imager array. The imager module 150 also includes a lens stack 112, which includes at least one lens element 111 with at least one corresponding lens carrier 110. The lens carrier 110 maintains the lens element 111 at a proper distance from the imager array 106, such that a desired amount of light striking a convex side of the lens element 111 is directed through an aperture to the imager array 106. The lens carrier 110 may be bonded to the imager die 108 by a bonding material 104 such as epoxy. Typically, the lens element 111 comprises an optically transmissive glass or plastic material configured to focus light radiation onto imager array 106. In addition, the lens structure 112 can include multiple lenses, or may be combined with another optically transmissive element, such as a package lid. The fabrication of one imager module and associated lens support structure is discussed in co-owned U.S. patent application Ser. No. 11/605,131, filed on Nov. 28, 2006 and U.S. patent application Ser. No. 12/073,998, filed on Mar. 12, 2008, which are hereby incorporated by reference.
One consideration in the manufacture of image modules of the type illustrated in FIG. 1 is the process by which the lens carrier 110 is attached to the imager dies 108. Wafer level packaging (WLP) is a preferred method of packaging semiconductor components because it produces smaller form factors, higher output and lower cost devices. Thus, although FIG. 1 shows one imager module 150, in practice, image die 108 is part of a larger imager wafer containing many such dies, and the lens carrier 110 and lens element 111 are part of a larger lens wafer containing many such lens carriers 10 and lens elements 111. The lens carrier wafer and imager die wafer are bonded together to form many imager modules 150 that are then separated by a dicing operation. However, using wafer level processes to produce imager modules 150 is challenging.
One consideration in the fabrication of image sensor semiconductor components is how to protect against damage to the imager array 106 and associated integrated circuits within dies 108. Another consideration is how to fabricate and connect lens elements, and associated lens carrier structures to a wafer containing imager dies. It is necessary for the lens elements and the associated carrier structures to protect the integrated circuits, and to provide desired optical characteristics as well. It is also advantageous for the lens elements and the associated carrier structures to be capable of providing electrical paths for the integrated circuit with a die. It would also be advantageous to provide structures and/or associated carrier structures which would reduce the influence of electromagnetic interference (EMI) and electro static discharge (ESD) on circuit operations. Additionally, it would be advantageous to eliminate a shear or other debond process which occurs during fabrication when a temporary carrier wafer is used and needs to be separated from another wafer to which it is attached during certain processing operations.